I have my doubts about how well “Love Never Dies” — the sequel to “The Phantom of the Opera” — will do on Broadway.

But there’s one show I saw last week in London that’ll play like gangbusters in New York. It’s called “London Assurance,” and it’s the funniest thing I’ve seen since Marcia Gay Harden jumped on James Gandolfini‘s back in “God of Carnage.”

Never heard of it?

Not many “civilians” (as theater people call non-theater people) have. Written by Dion Boucicault in 1841, this Victorian farce has been revived, with tremendous wit and style, by director Nick Hytner at London’s National Theatre.

The leads — Simon Russell Beale and Fiona Shaw — have appeared regularly in New York, although usually in the serious classics.

Beale starred in “The Cherry Orchard” at BAM last year, and Shaw was nominated for a Tony a few years ago for “Medea” (not a lot of laughs in that one).

Here they’re hamming it up to a fare-thee-well — and, it seems, having the times of their lives.

At the opening-night performances, I kept an eye on London’s major drama critics, a morose and haggard-looking gallery of old newspapermen.

(Hytner stirred up a hornet’s nest a few years ago when he called them “dead white men” who “don’t know it’s happened to them, but it has.”)

The critics were laughing like giddy kids.

Michael Billington, in the Guardian, called it “sprightly and vibrant,” Paul Taylor, in the Independent, called it “deliriously funny,” and John Peter, in the Sunday Times, said, very Englishly, that it was “unmissable.”

“London Assurance,” which made Boucicault’s name and fortune when he was 21, gets its big laughs from a collision of city slickers and country bumpkins. The characters have the kinds of Restoration-style comic names that make you chuckle when you open the program: Meddle (a lawyer), Pert (a maid), Cool (a valet), Dazzle (a swindler), Solomon Isaacs (a moneylender, of course) and the fabulous Lady Gay Spanker.

Beale plays Sir Harcourt Hartley, a West End dandy who’s 57 but claims to be 39 — and whose hair is shoe polish black. Dressed in plum coats and lime-green pants, he flounces around the stage looking like a fat, gay Napoleon.

Shaw plays Gay Spanker, a strapping country lady who looks like the horses she rides.

Sir Harcourt and Lady Gay’s sexuality is, in the production, up for grabs. But the farce kicks into high gear when he falls (improbably, hilariously) head over heels for her.

The National, which has shipped plenty of hits to Broadway, including Alan Bennett‘s “The History Boys,” did not, I’m sure, produce this old play with any idea of bringing it to New York.

But it’s just the kind of stylish, camp, 19th-century comedy that the British do so well — and Americans tend to screw up.

(Frank Langella‘s the only American actor I can think of who can play, effortlessly, the English fop.)

Broadway’s been inundated with British shows in the past year, and some theater people think they’re all beginning to cannibalize each other.

But “London Assurance” will stand out in any crowd. New York producer Bob Boyett has a deal with the National to bring productions over here. He hasn’t seen this one yet, but he should.

If he doesn’t bring it over, I will!

MANY of the “dead white male” critics referred in their reviews to a famous 1974 revival of “London Assurance” starring Donald Sinden.

A great raconteur, Sinden, speaking to Charles Spencer, in the Telegraph, last week, offered this anecdote, which I think is too priceless not to bring home.

The great actor Donald Wolfit once abused a young actor in a long-ago production of “Macbeth.”

But the actor got his revenge on the final night of the show.

Instead of delivering the line, “The Queen, my Lord, is dead,” he smiled and said: “The Queen, my Lord, is very much better.”